This invention relates to an ignition angle advancing mechanism for internal combustion engines, and more particularly to an improved ignition timing system and method.
Most internal combustion engines embody an ignition timing mechanism for timing the ignition so as to achieve maximum torque throughout the engine load range. This is achieved commonly through the use of a throttle operated advance mechanism so that the spark advance is controlled in relation to throttle opening. For example, in outboard engines a timing plate carries the timing mechanism and is rotatably supported relative to the crankshaft for altering engine timing in response to throttle valve opening. The most commonly employed throttle timing advance curve has a fixed static advance that is maintain up until a predetermined throttle opening. Once this throttle opening is reached, the timing is advanced until a maximum timing advance is achieved and this is maintained until wide-open throttle. Under partial load running with the throttle less than fully opened, there is a relatively low combustion temperature and flame propagation in the chamber and the advance spark timing provided by conventional timing mechanism is desirable to achieve maximum torque. However, it has been discovered that under wide-open throttle conditions and maximum speed that there is sufficient flame propagation that performance and fuel economy are actually deteriorated by the maximum spark advance provided by conventional mechanisms.
It is, therefore, a principal object of this invention to provide an improved spark timing mechanism for an internal combustion engine.
It is a further object of this invention to provide a structure and method for controlling spark timing that permits maximum torque to be achieved throughout the engin speed and load ranges.
It is a further object of this invention to provide an improved, simplified spark timing mechanism that will achieve the desired spark timing consistent with engine requirements.